Morphological, Molecular and Ecological Characterization of a Native Isolate of Steinernema Feltiae (Rhabditida: Steinernematidae) From Southern Chile

Abstract

Background: Steinernema feltiae is an entomopathogenic nematode used in biological control programs with a global distribution. It has been shown that populations of S. feltiae may have phenotypic plasticity derived from local adaptation and may vary in different traits, such as location and penetration of the host. This is the first time that a Chilean isolate has been described in detail, taking into account morphological, molecular and ecological characteristics. Methods: S. fealtiae was detected a few years ago in southern regions of Chile in the town Lican Ray and was morphologically and morphometrically described, along with a molecular description based on the ITS and D2-D3 regions. Some ecological characteristics were determined, including the temperature requirements for completion of its life cycle and the effect of three water levels in soil for optimal reproduction. Results: Morphometric characteristics of different life stages show large intraspecific variability in averages and ranks compared with isolates from different geographical origins. The molecular data also show intraspecific variability with respect to other isolates. The lower, optimal and higher temperatures found to limit the infestation and reproduction of Galleria mellonella were 10, 20 and 30 °C respectively, and emergence from the host larvae occurred approximately ten days after inoculation. Differences were observed in offspring emerging from the host, and the 120 infective juveniles (IJ)/larvae dose was the most prolific at 20 °C. The water content of the soil did not affect the number of infective juvenile invaders, penetration efficacy (%), and time of emergence of the IJ or offspring per larvae, but it caused a delay in achieving full mortality at the permanent wilting point with respect to saturation and field capacity.Conclusions: Data obtained in this study are valuable since they outline some environmental requirements of this strain to perform optimally in the event of being used as a soil pest bioantagonist.